Dosage compensation is the process by which the expression of X-linked genes is altered in one sex to counterbalance the difference in X-chromosome and autosome number in the heterogametic sex. Degeneration of the non-recombining Y chromosome is a general facet of sex chromosome evolution. Selective pressure to equalize expression levels of X- linked genes in males accompanies Y-chromosome degeneration, thus driving the evolution of dosage compensation. Drosophila miranda - a species for which we recently generated a de novo genome sequence assembly - has three sex chromosomes of different age and at different stages of transition from ordinary autosomes into heteromorphic sex chromosomes. Specifically, X-L is the ancestral sex chromosome of the genus Drosophila and >60MY old, X-R is shared by members of the D. pseudoobscura subgroup and >10MY old, while its neo-sex chromosome (about 1MY old) still largely resembles an autosome, but the neo-X is evolving partial dosage compensation. D. miranda therefore provides a unique system to study the evolution of dosage compensation in action using a comparative and functional genomics approach. We will use ChIP-seq techniques together with whole-genome population analysis to functionally characterize the targeting of the dosage compensation complex to the X chromosome, and how it evolves.